Conventionally, to control power transmission among three or more electric devices using a power conversion device, it has been necessary to provide power conversion devices for the individual electric devices. A small-sized and light-weight power conversion device at low cost having a function of controlling power transmission among three or more electric devices is needed.
To solve this problem, a power conversion device is disclosed which includes a transformer having three or more coils magnetically coupled with each other and controls AC voltage to be applied to each coil, using a full-bridge circuit provided for each coil (for example, Patent Document 1). Another power conversion device is disclosed which controls power transmission between first and second electric devices by a bidirectional chopper composed of an inductor and a half-bridge circuit having switching elements, and uses the inductor as a secondary-side coil of a transformer, to enable power supply to a third electric device (for example, Patent Documents 2, 3). Also, a power conversion device using a step up/down bidirectional chopper instead of the above bidirectional chopper is disclosed (for example, Patent Document 4). Still another power conversion device is disclosed in which power transmission between first and second electric devices and power transmission between a third electric device and the first or second electric device are temporally separated from each other and the self-inductance of a transformer is switched in accordance with the situation (for example, Patent Document 5).